The present invention relates to a copier, printer, facsimile apparatus or similar image forming apparatus and more particularly to a paper feeder for use in an image forming apparatus.
A paper feeder for use in an image forming apparatus generally includes a feed roller and a separating member that nip paper sheets being paid out together there between so as to separates them. Conventional paper separation systems are generally classified into two types, i.e., a roller type system and a friction pad type system. The roller type system includes a feed roller rotatable in a direction of a paper feed and a reverse roller pressed against the feed roller. A drive mechanism causes the reverse roller to rotate via a torque limiter in a direction opposite to the above direction. So long a single paper sheet is paid out to a nip between the feed roller and the reverse roller, the reverse roller follows the rotation of the feed roller via the torque limiter. When two or more paper sheets arrive at the nip together, the reverse roller rotates in the direction opposite to the direction of paper feed to thereby separate the paper sheets from each other. The friction pad type system includes a friction pad in place of the reverse roller as well as the feed roller. The friction pad is pressed against the feed roller in order to separate paper sheets being conveyed together by the feed roller.
Assume that paper sheets closely adhere to each other due to static electricity or irregular cut edges thereof, or that coated paper sheets or similar highly smooth paper sheets closely adhere to each other due to vacuum or high humidity. Then, the coefficient of friction between the paper sheets is apt to exceed the coefficient of friction between the feed roller and the reverse roller or the friction pad. In this condition, the conventional separation systems are apt to fail to surely separate paper sheets being paid out together.
To solve the above problem, Japanese Patent Laid-Open Publication No. 6-100179, for example, proposes a paper feeder that applies vibration to paper sheet stacked on a tray in order to loosen the paper sheets. However, causing a stack of paper sheets to vibrate is not practicable without resorting to vibration and force, which are extremely intense, and therefore without resorting to an expensive mechanism.
Japanese Patent Laid-Open Publication No. 5-201571 teaches a paper feeder including a feed roller fixed in place and a piece of separating sheet movable back and forth in a direction of paper feed in a vibrating fashion, thereby enhancing the separation of paper sheets. However, the vibration of the separating member moving back and force in the above direction is scarcely transferred to paper sheets and cannot loosen the paper sheets. The separating ability achievable with the separating member is only of the same degree as one achievable with the reverse roller.
Further, Japanese Patent Laid-Open Publication No. 5-213468 discloses a paper feeder including a feed roller fixed in place and a separating member vibratable up and down in order to delicately vary a force acting against paper conveyance. Such a separating member can be implemented as a pad having a great coefficient of friction and allows the separating ability to vary in matching relation to paper sheets on the basis of control over vibration. This kind of scheme is effective when the pad pressure is suppressed in order to vary the separating condition. However, the vibration is applied to paper sheets before separation and therefore cannot sufficiently loosen the paper sheets.
Technologies relating to the present invention are also disclosed in, e.g., Japanese Patent Laid-Open Publication No. 5-330683.
It is therefore an object of the present invention to provide a paper feeder capable of applying vibration to paper sheets being paid out together to thereby reduce an adhering force acting between the paper sheets and prevent them from being fed together, and an image forming apparatus including the same.
In accordance with the present invention, a paper feeder for separating paper sheets from each other while conveying the paper sheets includes a feed roller configured to rotate by being driven. A separating member is pressed against the feed roller. The paper sheets are nipped between the feed roller and the separating member. A vibration generating device applies vibrations, which are synchronous to each other, to the feed roller and separating member.
Also, in accordance with the present invention, an image forming apparatus includes a paper feeder including a feed roller driven to rotate and a separating member pressed against the feed roller for conveying paper sheets nipped between the feed roller and the separating member while separating them from each other. A vibration generating device applies vibrations, which are synchronous to each other, to the feed roller and separating member.
Further, in accordance with the present invention, a paper feeder for separating paper sheets from each other while conveying the paper sheets includes a feed roller driven to rotate and a separating member pressed against the feed roller. The paper sheets are nipped between the feed roller and the separating member. A vibration generating device applies vibration to the feed roller. The feed roller causes the separating member to vibrate when caused to vibrate by the vibration generating device.
Moreover, in accordance with the present invention, an image forming apparatus includes a paper feeder including a feed roller driven to rotate and a separating member pressed against the feed roller for separating paper sheets from each other while conveying them. The paper sheets are nipped between the feed roller and the separating member. A vibration generating device applies vibration to the feed roller. The feed roller causes the separating member to vibrate when caused to vibrate by the vibration generating device.